Interop: on signup, allow using BTC SPV proofs to autonomously trade BTC for an ERC20
BTC version: build directly on top of the LN
BTC version: re-implement OUTPACE on top of BTC; this will end up looking a lot like the LN, and will be really simple for the most part, except for the need of RSMC
there's a bunch of ways we can either do a BTC verison or implement BTC interoperability